Definition
Oribacterium is a genus of Gram‑positive, obligately anaerobic bacteria classified in the family Lachnospiraceae (order Clostridiales).
Overview
The genus was established in the early 21st century following the isolation of several species from human oral specimens, including subgingival plaque and the sinus cavity. Recognised species include Oribacterium sinus and Oribacterium catoniae. Members of this genus are part of the normal oral microbiota but have also been detected in clinical samples associated with periodontal disease and sinus infections. Molecular phylogenetic analyses based on 16S rRNA gene sequences place Oribacterium within the Lachnospiraceae, a family that comprises many fermentative, anaerobic gut and oral bacteria.
Etymology/Origin
The generic name appears to be derived from the Latin root orib‑ (pertaining to the mouth) combined with the suffix ‑bacterium (rod‑shaped bacterium). Accurate etymological details have not been explicitly published; the above interpretation is consistent with the typical naming conventions for oral bacteria.
Characteristics
| Feature | Description |
|---|---|
| Cell morphology | Straight or slightly curved rods; non‑spore‑forming; typically 0.5–1 µm in width and 2–4 µm in length. |
| Gram reaction | Positive (thin peptidoglycan layer with teichoic acids). |
| Oxygen requirement | Obligate anaerobe; growth only under strictly anaerobic conditions. |
| Metabolism | Fermentative; metabolises carbohydrates to short‑chain fatty acids (e.g., acetate, propionate) and gases (CO₂, H₂). |
| Catalase/oxidase | Catalase‑negative; oxidase‑negative. |
| Growth media | Grows on enriched anaerobic agar such as blood agar or Schaedler medium supplemented with hemin and vitamin K. |
| Genomic features | 16S rRNA gene sequences share ≥ 95 % identity with other Lachnospiraceae; whole‑genome sequencing of type strains reveals genes for carbohydrate‑active enzymes typical of oral saccharolytic bacteria. |
| Ecological niche | Predominantly isolated from the human oral cavity (tongue, gingival crevices) and occasionally from sinus aspirates. |
Related Topics
- Lachnospiraceae – the bacterial family to which Oribacterium belongs.
- Human oral microbiome – the complex community of microorganisms inhabiting the mouth, of which Oribacterium is a component.
- Anaerobic bacteria – a broad group of microorganisms that thrive in oxygen‑depleted environments.
- Periodontal disease – inflammatory conditions of the gums where shifts in the oral microbiota, including increased Oribacterium abundance, have been reported.
- Clostridiales – the order encompassing many fermentative, anaerobic bacteria, including the Lachnospiraceae.
Note: Information presented reflects current peer‑reviewed literature and taxonomic databases as of 2026. Where specific details (e.g., etymology) are not explicitly documented, the most plausible interpretation is provided with the caveat that it has not been formally confirmed.